Generally, a typical electrical connector includes some form of dielectric or insulative housing which mounts a plurality of conductive terminals. It is well known to provide electrical connectors mounted to a printed circuit board, with contact terminals therein electrically coupled to respective electrical circuit traces on the board. The terminals typically have solder tails projecting from the connector and inserted into holes in the board, or the terminals may have leg portions generally parallel to the board for surface mounting in electrical engagement with circuit pads on the board. In either instance, the terminals are coupled to the circuit traces on the board most commonly by solder connections, either between the solder tails and plated through-holes in the board or between the surface mounted leg portions and the circuit pads on the board surface.
Circuit board mounted electrical connectors of the character described above typically have the terminals mounted in the connector housing such that the solder tails or the surface mounted leg portions are arranged in rows for solder connection to rows of plated through-holes in the board or rows of circuit pads on the board surface. In high density or fine pitch connectors, a single row of terminals in a housing may have solder tails arranged in two separate staggered rows. Unfortunately, staggering solder tails can lead to problems in high speed applications due to the fact that adjacent terminals have different electrical path lengths. Such different electrical path lengths may result in undesirable signal skew in some applications.
Surface mounted terminals generally provide better electrical performance than the through-hole terminals because the surface mount pads to which the surface mounted terminals are soldered have less capacitance than the through holes to which the through hole terminals are soldered. The capacitance of the through holes can create impedance problems detrimental to the integrity of high-performance signals. Additionally, surface mount pads can be laid out "on pitch" or closer together than through holes thus negating the need to stagger solder tail portions. Consequently, adjacent terminals with surface mount tail portions can have equal electrical path lengths which is also beneficial in high speed applications. Therefore, high performance or high speed terminals are often best configured with surface mounted leg portions.
On the other hand, surface mounted leg portions have a greater tendency to strip off of the circuit pads on the board surface when the terminals are subjected to undesirable shearing forces. Through-hole solder tails provide considerably more mechanical strength at the interconnection interfaces between the terminals and the through holes of the board.
It has been known to provide an electrical connector with a row of terminals with through-hole solder tails as well as a row of terminals with surface mounted leg portions. However, such hybrid row configurations place considerable limits on the circuit design variables of the electrical connector. The present invention is directed to solving the problems or dilemma described above by providing an electrical connector with a unique, versatile terminal arrangement.